An inkjet printhead is a device used to produce a predetermined image by discharging or ejecting small ink droplets on a desired location on a printing medium. An inkjet printhead can be classified into two types based on the mechanism that is used for discharging the ink droplets. A first type is a thermal inkjet printhead that generates ink bubbles using a heat source and discharges or ejects the ink droplets as a result of an expansive force produced by the bubbles. A second type is a piezoelectric inkjet printhead in which a piezo-electric material is used and the ink droplets are discharged or ejected by pressure applied to the ink by a transformation or deformation of the piezo-electric material.
Below is described a mechanism for discharging ink droplets in a thermal inkjet printhead.
During an electrical pulse, current flows through a heater that includes a heating resistor. As a result of the current applied, heat is generated in the heater and ink that is adjacent to the heater is rapidly heated up to about 300 degrees Celsius (° C.). The ink boils to generate ink bubbles such that the ink bubbles expand and apply pressure to the ink that is within an ink chamber. Thus, the ink in the ink chamber that is adjacent to a nozzle is discharged or ejected from the ink chamber and through the nozzle in the form of ink droplets.
The thermal inkjet printhead can have a structure in which a chamber layer and a nozzle layer are disposed on a substrate (e.g., by sequential lamination or layering). The substrate is such that multiple layers of materials can be formed or disposed on the substrate. The chamber layer includes multiple ink chambers, each being configured to hold or be filled with ink to be discharged. The nozzle layer includes multiple nozzles through which ink from an associated ink chamber from the chamber layer is discharged. An ink feed hole for applying ink to the ink chambers is formed through the substrate. The ink feed hole can be configured such that the flow of ink to each of the ink chambers is substantially the same.